The present invention relates to a method for preparing cooked rice with barley in an aseptic packing process, comprising mixing barley, which had been sterilization-treated and then dried, with non-glutinous rice. The method for preparing cooked rice with barley in an aseptic packing system according to the present invention is characterized in that by using barley that has been first gelatinized and then retrogradated, the cooked rice with barley has a reduced initial level of microorganisms in the barley, leading to excellent stability against microorganisms, a long storage life, of 6 months or longer at ambient temperature, excellent appearance, pleasant flavor, and soft, flexible, and sticky texture.